1. Field of the Invention
The present invention relates to a one-pin dynamic electron gun for a cathode ray tube having an improved voltage efficiency applied to its dynamic electrode.
2. Description of the Related Art
As a way to reduce power consumption of a cathode ray tube, a neck having a smaller diameter has been used and, as a result, there is not much room to install a stem pin, which required a one-pin type dynamic electron gun.
FIG. 1 illustrates a conventional one-pin dynamic electron gun. FIG. 2 shows a schematic diagram of the electron gun shown in FIG. 1. It is composed of a cathode 11 emitting electrons and a plurality of electrodes G to focus and accelerate the emitted electrons. G1, G2, G3, G4, G5xe2x88x921, G5xe2x88x922 and G6 are a control electrode, screen electrode, first focus electrode, second focus electrode, third focus electrode, fourth focus electrode and anode electrode, respectively. Ec1, Ec2, Vf+Vd, and Eb represent voltages applied to the corresponding electrodes.
In the above electron gun, Vd is supplied from an external voltage source and the effective voltage Vd (eff) between the third focus electrode G5xe2x88x921 and the fourth focus electrode G5xe2x88x922 is equal to Vdxe2x88x92Vg, where Vg has a gain and phase difference xcfx86 with respect to Vd according to the following formula 1:                                                         Vg              =                              Vd                ⁢                                                                            1                      +                                                                        (                                                      ω                            ⁢                                                          xe2x80x83                                                        ⁢                            C1R1                                                    )                                                2                                                                                    1                      +                                                                                                                                  ω                              2                                                        ⁡                                                          (                                                              C1                                +                                C2                                                            )                                                                                2                                                ⁢                                                  R1                          2                                                                                                                                                                                            φ              =                                                tan                                      -                    1                                                  ⁢                                  xe2x80x83                                ⁢                                                                            -                      ω                                        ⁢                                          xe2x80x83                                        ⁢                    C2R1                                                        1                    +                                                                  ω                        2                                            ⁢                                              C1                        ⁡                                                  (                                                      C1                            +                            C2                                                    )                                                                    ⁢                                              R1                        2                                                                                                                                                    [                  Formula          ⁢                      xe2x80x83                    ⁢          1                ]            
where C1 represents capacitance between the third focus electrode G5xe2x88x921 and the fourth focus electrode G5xe2x88x922 due to the distance between them, and C2 represents capacitance between the second focus electrode G4 and the third focus electrode G5xe2x88x921 due to the distance between them and has a similar value to C1. Assuming C1=C2, for a horizontal deflection signal of 64 KHz in frequency, Vg is equal to one half of Vd and the effective dynamic voltage Vd (eff)=Vdxe2x88x92Vd/2=Vd/2. This implies that power efficiency of Vd delivered between the third and fourth electrodes is only 50%. And there is almost no phase difference, i.e., 0.14 degree. Although a dynamic voltage according to the vertical deflection signal is currently not supplied from the external source, if it is to be in the future, Vg will be 0.95 Vd for a 60 Hz vertical deflection signal, meaning that the power efficiency is only 5%, resulting in the electrodes failing to function as a quadrupole lens.
To solve the above problems, it is an objective of the present invention to provide a first objective of the present invention is to maximize power efficiency of a voltage signal applied to a dynamic electrode of an electron gun.
A dielectric is installed between the second focus electrode and third focus electrode in a one-pin dynamic electron gun assembly in order to increase capacitance between the two electrodes. The increased capacitance between the two electrodes reduces the voltage Vg therebetween and increases the effective voltage Vd (eff) between the third focus electrode and fourth electrode since Vd (eff) =Vdxe2x88x92Vg.